1. Field of the Invention
The present invention relates to a message transmission system, and more particularly, to a control apparatus and method for relay node duplexing.
2. Description of the Background Art
Generally, in a system for switching messages between processors, such as a system for switching HDLC (High Level Data Link Control) messages between processors and a system for switching ethernet messages between processors, a node system for relaying messages is constructed as a duplex structure in order to provide the stability of system operation.
FIG. 1 is a block diagram of the construction of a system for switching messages between processors.
As shown in FIG. 1, a switching device 200 performs the function of IPC (Inter Processor Communication) between processors 100-1 through 100-n. An U-LINK interface cable for supporting the full-duplex transmission mode is connected between the switching device 200 and the processes 100-1 though 100-n. The switching device 200 is formed in such a manner that a number of modes nodes 230A1–230An and 230B1–230Bn are connected to one D-BUS (switching unit) 210. In addition, each node 230A1–230An and 230B1–230Bn is connected to its respective processor 100-1 through 100-n. And, one processor is connected with 2 nodes.
The switching device 200 is constructed as a redundancy duplex structure wherein a B-side node 200B is in the standby state during the operation of an A-side node 200A. The A-side node 200A receives power from a power supply A 220A, and the B-side node 200B receives power from a power supply B 220B.
The processors 100-1 through 100-n send the same message to both A-side node 200A and B-side node 200B, in order to provide a duplex IPC path.
FIG. 2 is a block diagram of the construction of duplex nodes (230A, 230B) positioned at the switching device 200.
The node A 230A and node B 230B are constructed as the in a redundancy duplex structure. Switching unit 210 switches messages between the nodes and a D-BUS, and the nodes are connected to the processors through a U-LINK. The duplex node A 230A and node B 230B receive messages from the processors through the U-LINK to thus relay the same to the D-BUS, and receives messages from the D-BUS to thus relay the same to the U-LINK. The message through the U-LINK is a 1 bit serial data, and the message through the D-BUS is a number of bits (for example, 8 bits or 16 bit or 32 bits) of parallel data.
The node A 230A and node B 230B performs duplexing function by transmitting a signal (NODE_FAIL) representing that the node cannot be operated any more and a signal (NODE_ACT) informing that the node has an active right to its opposite node. In addition, a power fail signal for informing that there occurs a failure in power supply.
FIG. 3 is a block diagram of the construction of one node.
As shown therein, the node includes a duplexing control unit 234 for controlling redundancy duplexing; a node control unit 233 operated according to the control of the duplexing control unit 234 and for performing message relay function by interfacing by means of a processor and a U-LPK and interfacing by means of the switching unit 210 and a D-BUS, receiving buffer (RX buffer) 232 for buffering a message to be transmitted from the processor to the switching unit 210 according to the control of the node control unit 233, and a transmission buffer (TX buffer) 231 for buffering a message to be transmitted from the switching unit 210 to the processor according to the control of the node control unit 233.
The duplexing control unit 234 receives a power fail signal from the corresponding power supply, and sends and receives a duplexing-related signal (NODE_ACT and NODE_FAIL) to and from the opposite node.
The node control unit 223 includes: and U-LINK interface having an U-LINK transmission interface (UTX interface) 233a for transmitting a message to a processor by means of an U-LINK interface and a U-LINK receiving interface (URX interface) 233a for receiving a message from the processor by means of the U-LINK interface, according to the control of the duplexing control unit 234; and a D-BUS interface having a D-BUS receiving interface (DRX interface) 233c for receiving a message from a switching unit 210 by means of a D-BUS interface and a D-Bus transmission interface (DTX interface) 223d for transmitting a message to the switching unit 210 by means of the D-BUS interface, according to the control of the duplexing control unit 234.
The TX buffer 231 receives a message from the DRX interface 233a, buffers the same, and then transmits it to the UTX interface 233a, according to the control of the DRX interface 233c. The RX buffer 232 receives a message from the URX interface 233b, buffers the same, and then transmits it to the DTX interface 233d, according to the control of the URX interface 233b. 
The operation of the thusly described control apparatus for relay node duplexing according to the conventional art will now be described.
When the switching device 200 switches a HDLC message between processors, the duplex node performs the function of relaying the HDLC message. The message inputted into the switching device 200 is formed in a HDLC frame, said HDLC frame is formed to have a predetermined time period between frames. In other words, the node selects a transmission node in which other frames are note received for a predetermined time after receiving one frame, when it receives a HDLC message through the U-LINK or through the D-BUS. In addition, since the HDLC frame has a start flag and a complete flag (end flag) in its structure, the node can know the start and end of the message.
If the node A 230A is in the active node, and the node B B 230B is in the standby node, the node A-230A performs the function of receiving a message from the processor through the U-LINK to transmit the same to the switching unit 210 through the D-BUS, and transmitting a message from the switching unit 210 through the D-BUS to thus transmitting the same processor through the U-LINK. The node B 230B becomes the standby state.
The operation of the node A 230A will be described in more detail (here, to help in understanding, the node as shown in FIG. 3 is assumed to be the node A 230A.). In case of receiving a HDCL message from the processor through the U-LINK, the duplexing control unit 234 of the node A 230A applies an enable signal (URX_ENABLE) to the URX interface 233b. The URX interface 233b applies a signal (RX_START) informing that there is a received message to the RX buffer 232, and stores the received message to the RX buffer 232.
When the message is stored in the RX buffer, the duplexing control unit 234 applies an enable signal (DTX_ENABLE) to the DTX interface 233d. The DTX interface 233d reads the message from the RX buffer 232, and transmits the same to the switching unit 210 through the D-BUS.
On the contrary, when a HDLC message is received from the D-BUS, the duplexing control unit 233c outputs a signal (TX_START) informing that there is a message to be transmitted to the corresponding processor to the TX buffer 231, and stores the message received through the D-BUS in the TX buffer.
When the message is stored in the TX buffer 231, the duplexing control unit 234 applies an enable signal (UTX_ENABLE) from the UTX interface 233a. The UTX interface 233a reads the message from the TX buffer 231, and transmits the same to the processor through the U-LINK.
Afterwards, the node A 230A, e.g., the active node, becomes inoperable, a duplex exchange for translating the node B 230B in the standby mode into the active mode has to be done.
As an example of the occurrence of the inoperable state of the node A 230A, e.g., the active node, when a power fail is occurred, the active right is passed to the node B 230B, e.g., the standby node, and the node A 230A becomes inoperable. The node B 230B translated into the active state starts a message relay function by activating its node control unit.
The inactive node A 230-A stops the message relay function by disabling the node control unit 233.
Therefore, since the conventional control apparatus for relay node duplexing stops the message relay function of the active node, and performs exchange to the standby node, there occurs a problem that the message stored in the buffer of the active node before exchange is lost.
In addition, when the standby node becomes the active state by duplex exchange, it can perform the message relay functions. Thus, there occurs a problem that the message transmitted to the processor or the switching unit is lost during the exchange operation.